This invention relates in general to a control system for a machine and, in particular, to a control system which utilizes a single chip eight-bit microprocessor to control the operation of the machine.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a solid state machine control system which is particularly adaptable for use with a vending machine whereby information is received and transmitted throughout the system to effect operation of the vending machine.
The machine control system disclosed herein utilizes solid-state circuitry to provide a more reliable control system whereby maintenance or replacement of parts can be easily accomplished. A single chip eight-bit microprocessor is used herein to effect a unique control whereby information is received into the system by external means, such as, a customer depositing coins into a vending machine. The information is then transmitted to the microprocessor which will effect operation of the machine in accordance with a preselected or predetermined program which is stored in a programmable read only memory (PROM) which is within the control system of the machine. The program contained within the PROM comprises a set of instructions that dictate the manner in which the system will operate depending on various signals received into the system, such as, coins being deposited into the machine, actuation of a coin return switch or depression of a key switch corresponding to a product desired to be dispensed from the machine.
The control system when used with a vending machine has the capacity to handle 42 different products. A 42 switch keyboard, with each switch corresponding to a different product contained within the machine, is coupled in a six by seven matrix. The control system has a plurality of price switches which permits the price of each product to be pre-set for any amount between $0.05 and $7.95, in increments of $0.05. The various key switches of the keyboard are operatively coupled to one of the price switches which corresponds to the price of the product which is to be dispensed upon actuation of the corresponding key switch. The control system also operatively couples a display or a readout panel which will visually display, to the customer, the amount of money he has deposited into the vending machine.
A price comparator, operatively coupled between the price selection switches and the readout panel, compares the amount of money present in the machine with the actual price of the product selected. In the event that the prices are not in agreement, the control system ignores the price selection switch output and waits for another signal, such as, additional coins being deposited, actuation of a coin return switch or actuation of another keyboard switch which corresponds to a different product coinciding with the amount of money deposited in the machine. When coincidence between the readout display and price selection switches is reached, the control system will begin a vend cycle to dispense the product selected.
To insure that the customer receives his product, the control system will wait for a dispense verification signal before collecting the coins deposited into a cash box. The dispense verification signal is transmitted when the product desired hits the dispensing tray. In the event that the particular product selected is sold out or for any other reason cannot or does not discharge from the machine, the dispense verification signal will not be received. If a dispense verification signal is not received, the coins deposited in the machine will be returned to the customer. The machine will in either situation be reset for a new cycle of operation.